Like its predecessors, the omap5 has a special bank of I/Os for interfacing with sdcards, which (unlike other I/O) may operate at 3V in addition to 1.8V, with support for switching at runtime.

Unfortunately the designated LDO for this supply in the PMIC (Palmas), LDO9, can only supply 50 mA while cards are known to require more than that in practice. I also suspect (but I'm not sure) that LDO9 may have been powered too early. The bizarre "solution" TI used on the omap5-uevm, which unfortunately has been copied by others, is: